Pulp digester



Feb. 7, 1928. 1,658,216

A. W. WAERN PULP DIGESTER Filed June 27'. 1927 :NWNTOR flda 1 0/; I44 1 141 errz A FT Patented Feb. 7, 1928.

UNITED STATES ADOLPH W. WAER'N, 013' ONTONAGON, MICHIGAN.

PULP DIGESTEB.

Application filed June, 1927. Serial No. 201,858.

This invention relates to pulp digesters.

In soda and sulphate pulp digesters, the digesting liquor is withdrawn from the bottom and pumped into the top of the digester.

The liquor may or may not be heated intermediate its withdrawal and recharging into the digester. When an outside circulating system for the liquor is used, a perforated false bottom is provided in the bottom or lower end of the digester to prevent the pulp chips or undigested material from following the circulating liquor and clogging the pump or piping.

It is difficult in digesters having an inside sloping false bottom to make a clean blow due to the fact that the wood chips, half or partly pulped are sucked against the false bottom and stick to the false bottom plates. As a result, a large uantity of the pulp does not blow out and is eft in the bottom of the digester. This condition, of course, very materially cuts down the efficiency of the digester since the capacity is decreased and unless the artly pulped chips are cleaned out by a re low, practically all the pulp left over will be destroyed during the next cooking,process.

Furthermore. in pulp'digesters having the usual form of false bottom there is a large dead space or waste space between the false bottom plates and the wall of the digester. This space contains no chips and thus reduces the capacity of the digester. Moreover, the space must be filled with liquor. thus increasing the required quantity of liquor and the steam consumption required to heat the liquor.

With the above difficulties in mind, this invention has for one of its objects to pro vide a pulp digester having afalse bottom so constructed and arrangedthat the digester Evfiill be thoroughly cleaned out during the Another object of the invention is to provide a construction of false bottom that will be easily accessible and can be readily removed, repaired and cleaned.

Another object of the'invention is to provide a false bottom for pulp digesters so constructed and arranged that the full capacity of the digester can be utilized for the charge.

Another object of the invention is to provide a false bottom so designed that all dead spacg and the attendant evils will be eliminate Another object of the invention is to provide a false bottom so designed that the parts thereof cannot become loosened and injure the liquor circulating system.

Further objects of the invention will ap pear from the following specification taken in connection with the drawings, which form a part of this application, and in which Fig. 1 is an elevational view of a digester and liquor circulating system constructed in accordance with the invention;

Fig. 2 is a sectional elevation of the lower end of the digester shown in Fig. 1;

Fig. 3 is a sectional elevation similar to Fig. 2 but showing a false bottom construction for digesters having a square bottom;

Fig. 4 is a sectional elevation of the screen utilized in the false bottom constructed in accordance with the invention; and

Fig. 5 is a to plan view of the construction shown in ig. 4.

The invention briefly described consists of a pulp digester having a sloping lower end provided with a centrally disposed discharge outlet and a casing secured to the bottom of the digester around the discharge opening. The casing is preferably substantially cylindrical and a substantially cylindrical screen is mounted therein. The circulating liquoris withdrawn from the casing and is umped back into the top of the digester. bottom-plate is secured to the lower end of the casing and is dished or downwardly inclined and has a discharge opening through which the digested pulp is discharged during the blow. Further details of the invention will appear from the following description.

The invention may be utilized with anytype of pulp digester and in the drawings there is shown a digester 10 having a false bottom casing 11 secured to the lower end thereof, a pipe 12 secured to the false bot tom "casing and withdrawing the liquor therefrom by means of a pump 13. The pipe 12 is provided with a check valve 9 to prevent the pressure from the top of the digester reaching casing 11 through the circulating system. The pump discharges the liquor through a pipe 14 into a heater 15 which heats the liquor and the liquor is pumped from the heater. through pipes 16 and 17 back into the top of the digester.

In the form of the invention illustrated in Figs. 1 and 2, the lower end 20 of the digester is tapered and is provided with a con gester 10 around the discharge opening 21.

A substantially cylindrical screen is mounted in the casing 11 and has a flange 31 at the lower end secured between a bottom plate 32 and the lower end of the easing 11. The bottom plate and screen may be secured by bolts 33. The inner diameter of the screen is substantially the same as the inner diameter of the reduced portion 25 of the casing 11 and as shown in Fig. 2, the upper end of the screen is disposed within an annular shoulder 34 formed between the reduced portion of the casing and the remaining portion thereof. The screen, therefore, forms an annular chamber 35 in the casing.

The flange 31 of the screen is provided with a plurality of conduits 38 which communicate with the annular chamber 35 and conduct thereto steam from steam pipes 39.

The bottom plate 32 of the casing 11 has a central discharge opening 40 and has connected thereto a blow-out valve 41- connected to a blow pipe 42.

The construction shown in Fig. 3 is substantially the same as that illustrated in Figs. 1 and 2 except that the bottom 45 of i the digester is square and a sloping bottom 46 is mounted within the bottom 45. The bottom 46 is not perforated but consists of plates supported on steel beams such as T- beams 47. Thespace between the supplemental bottom 46 and the square bottom 45 of the digester is preferably filled with concrete 48. This construction gives in effect the same results as those obtained by the sloping bottom 20 of the digester 10 shown in Figs. 1, and 2 and the structure shown in Fig.3. is merely illustrated to show how a square bottom digester can be changed or modified to adapt it for use with the improved false bottom device.

In the operation of the false bottom device, the digesting liquor is sucked through the-screen 30 into the chamber 35 surrounding the screen and is pumped out of this chamber through the pipe 12. Since the screen is substantially vertical, it will not become clogged and partially digested pulp chips will not be caused to adhere thereto by the suction of the circulating liquor. With this device, the digested pulp will be thoroughly cleaned out of the digester during the blow. Furthermore, in case it becomes necessary to clean or repair the false bottom device, the entire device can be unbolted from the bottom of the digester and the parts thereof will be readily accessible or by removing the bottom plate 32, the screen can be vertically withdrawn from the casing, giving ready access to the parts to be cleaned or rep aired.

With the present forms of false bottoms it is necessary in order toclean or repair the parts for workmen to descend into the digester and to work therein. Moreover, although with the present forms of false bottom, parts become loose and cause damage by being sucked into the circulating system, the nature of the design of the false bottom device above described eliminates loosening of parts or damage caused thereby.

Although certain specific embodiments of the invention have been particularly shown and described, it will be understood that the invention is, capable of modification and that changes in the construction and in the arrangement of the various cooperating parts may be made without departing from the spirit or scope of the invention, as expressed in. the following claims.

What I claim is:

1. A pulp digester having a discharge opening at the lower end thereof, a casing secured to the bottom of the digester around the discharge opening, a screen in said casing and spaced from the walls thereof, and a liquor, circulation suction conduit communicating with said casing, said casing having a discharge opening atthe bottom thereof.

2. A pulp digester having a discharge opening at the lower end thereof, a casing secured. to the bottom of the digester around the discharge opening, a substantially cylindrical screen in said casing and spaced from the walls thereof, and a liquor circulation suction conduit communicating with said casing, said casing having a discharge opening at the bottom thereof.

3. A pulp digester having a discharge opening at the lower end thereof, a casing secured to the bottom of the digester around the discharge opening, an openended screen in said casing and spaced from the walls thereof, and a liquor circulation suction conduit communicating with said casing, said casing having a discharge opening at the bottom thereof.

4; A pulp digester having a discharge opening atthe lower end thereof, a casing secured to the bottonrof the digester around the discharge opening. a substantially cylindrical, open-ended screen in said casin .and spaced from the wallsthereof, and a fiquor circulation suction conduit communicating with said casing, said casing having a. discharge opening at the bottom thereof.

5. A pulp digester having a discharge opening at the lower end thereof, a casing detachably secured to the bottom of the digester around the discharge opening, a screen in said casing and spaced from the walls thereof, and a liquor circulation suction conduit communicating with said casing, said casing having a discharge opening at the bottom thereof.

6. A pulp digester having a discharge opening at the lower end thereof, a casing secured to the bottom of the digester around the discharge opening, a bottom plate secured to the lower end of said casing and having a central discharge opening therein, and a screen having a fiange'secured between said bottom plate and easing, said screen extending upwardly substantially throughout the length of the casing.

7. A pulp digester having a discharge opening at the lower end thereof, a, casing secured to the bottom of the digester around the discharge opening, abottom plate secured to the lower end of said casing and having a central discharge opening therein, a screen having a flange secured between said bottom plate and easing, said screen extending upwardly substantially throughout the length of the casing and being spaced from the casing wall. I

8. A pulp digester having a discharge opening at the lower end thereof, a casing secured to the bottom of the digester around ing.

the discharge opening, a bottomplate secured to the lower end of said casing and having a central discharge openin therein, a substantially cylindrical screen having a flange secured between said bottom plate and easing, said screen'extending upwardly substantially throughout the length of the eas- 9. A pulp digester having a discharge opening at the lower end thereof, a casing secured to the bottom of the digester around the discharge opening, a bottom plate secured to the lower end of said casing and having a central discharge opening therein, an open-ended screen having a flange secured between said bottom plate and casing, said screen extending upwardly substantially throughout the length of the casing.

10. A pulp digester having a discharge opening at the lower end thereof, a casin secured to the bottom of the digester aroun the discharge opening, a bottom plate secured to the lower end of said casing and having a central discharge opening therein, a substantially cylindrical, open-ended screen having a flange secured between said bottom plate and easing, said screen extending upwardly substantially throughout the length of the casing.

11. A pulp digester having a discharge openin at the lower end thereof, a casing secure to the bottom of the digester around the discharge opening, a bottom plate secured to the lower end of said casing and having a central discharge openin therein, a screen having a flange secure between said bottom plate and easing, said screen extending upwardly substantially throughout the length of the casing and being spaced from the casing wall, said flange having a conduit therethrough leading to the space between the screen and easing wall.

12. A pulp digester having adischarge opening at the lower end thereof, a casing secured to the bottom of the digester around the discharge opening, a downwardly sloping bottom plate secured to the lower end of said casing and having a central discharge opening therein, and a screen having a flange secured between said bottom plate and casing, said screen extending upwardly substantially throughout the length of the eas- 13. A pulp digester having a discharge opening at the lower end thereof, a casing comprising a cylindrical shell having a portion reduced in diameter and secured to the bottom of the digester around said opening,

.and a screen disposed in said shell, spaced from the major portion of the shell but substantially alined with the reduced portion thereof.

14. A pulp digester having a discharge opening atthe lower end thereof, a casing comprising a c lindrical shell having a ortion reduced in diameter and secure to the bottom of the digester around said opening, and a substantially cylindrical screen disposed in said shell, spaced from the major portion of the shell but substantially alined with the reduced portion thereof.

15. A pulp digester having a discharge opening at the lower end thereof, a casing comprising a cylindrical shell having a portionreduced in diameter and secured to the bottom of the digester around said opening, and a substantially cylindrical, open-ended screen disposed in said shell, spaced from the major portion of the shell but substantially alined with the reduced portion thereof.

16. A pul digester having a discharge opening at tie lower end thereof, a casing comprising a cylindrical shell having a portion reduced in diameter and secured to the bottom of the digester around said opening, a screen disposed in said shell, spaced from the major portion of the shell but substantiall alined with the reduced portion thereo and a bottom plate secured to said shell below said screen and having a central discharge opening therein.

17. A pulp digester having la discharge opening at the lower end thereof, a casing comprising a cylindrical shell havin a portion reduced in diameter and secure to the bottom ofthe digester around said opening, a screen disposed in said shell, spaced from the major portion of the shell but substantially alined with the reduced portion thereof, and a bottom plate secured to said shell below said screen and havin a central discharge opening therein, sai screen having a flange secured to the bottom thereof and disposed between the lower end of, the shell and said bottom plate.

18. A pulp digester having a discharge opening at the lower end thereof, a casing shell secured to the bottom of the digester and around the'discharge opening thereof, a screen in said shell'and spaced from the wallthereof, and a bottom plate secured to said shell below said screen and having a central discharge opening therein.

19. A pulp digester having a discharge opening at tie lower end thereof, a casing she'll secured to the bottom of the digester and around the discharge opening thereof, a screen in said shell and spaced from the wall thereof, and a bottom plate secured to said shell below said screen and having a central discharge opening therein, said screen havin a flan e secured to the bottom thereof and ispose between the lower end of the shell and said bottom plate. 20. A pul digester having a discharge opening at t e lower end thereof, a casing shell secured to the bottom of the digester and around the discharge opening thereof, a screen in said shell and spaced from the wall thereof, a bottom plate secured to said shell below said screen and'having acentral discharge opening therein, and "means for conductlng steam to the space between the screen and the casing. v

In witness whereof, I have hereunto set my hand this 14th day of June, 1927.

ADOLPH W. 'WAER'N. 

